# Dictionary:Pseudosection

(soo, dō sek’ sh∂n) **1**. A plot of electrical measurements or calculations, often of apparent resistivity or induced polarization as a function of position and electrode separation (which is nonlinearly related to the *depth of investigation*, q.v.). A pseudosection indicates how the parameter varies with location and depth, but it can only be converted into a 2D model by inversion. Also called a **quasi-section** or **pseudodepth section**. For the dipole-dipole electrode configuration, the data are plotted (Figure P-17) beneath the midpoint between the dipoles at a depth of half the distance between the dipole centers. For the Schlumberger array, the data are plotted beneath the potential electrodes at a depth of half the separation of the current electrodes (AB/2). **2**. For frequency-domain measurements, the vertical scale is sometimes increasing period (or decreasing frequency). **3**. Also used for plotting magnetotelluric apparent resistivity as a function of frequency (*z*-axis) and traverse distance (*x*-axis).